2-furylbutyrolactones and methods for using same

ABSTRACT

Novel 2-furylbutyrolactones are directly formed by reaction of 2,5-dialkoxy-2,5-dihydrofurans and 2,3-dihydroxybutenolides in aqueous media and recovering crystalline product from an anhydrous medium. These novel compounds and compositions containing same may be used for lymophocyte stimulation.

This application is a continuation-in-part of pending application Ser. No. 450,493, filed Dec. 16, 1982, now abandoned, which is in turn a continuation of application Ser. No. 192,806, filed Oct. 1, 1980, now abandoned, which is in turn a divisional of application Ser. No. 093,594, filed Nov. 13, 1979, now U.S. Pat. No. 4,287,205, which is in turn a continuation of Ser. No. 917,327, filed June 20, 1978, now abandoned.

RELATED CASES

This application is related to pending application Ser. No. 192,815, of Szent-Gyorgyi and Fodor, filed Oct. 1, 1980, now abandoned, which is in turn a divisional of application Ser. No. 093,594, filed Nov. 13, 1979, now U.S. Pat. No. 4,287,205, which is in turn a continuation of application Ser. No. 917,327, filed June 20, 1978, now abandoned.

This application is also related to application Ser. No. 536,993 of Fodor, filed concurrently herewith, now abandoned, which is in turn a continuation-in-part of application Ser. No. 478,331, filed Mar. 24, 1983, now abandoned, and to application Ser. No. 536,995 of Veltri, filed concurrently herewith, now U.S. Pat. No. 4,518,611, which is in turn a continuation-in-part of application Ser. No. 481,998, filed Apr. 4, 1983, now abandoned, which is in turn a continuation-in-part of application Ser. No. 449,584, filed Dec. 14, 1982, now abandoned.

U.S. Pat. No. 4,287,205 discloses subject matter related to the present invention, particularly in that starting reactants are overlapping. The reaction mechanism and the structure of the resulting compounds are, however, substantially different. The utility of the related, prior invention is closely related to that of the present invention.

It is believed that the present invention is much narrower in scope than the prior invention, and where the prior invention is applicable to a broad variety of enediol reactants, the present invention is limited to reactants where the enediol structure is a part of a 2,3-dihydroxybutenolide. While aldehyde or ketone reactants are defined in the prior patent, the present application is limited to 2,5-dialkoxy-2,5-dihydrofurans, which are the product of a ring closure of certain types of aldehydes and ketones of the prior cases.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 2,927,054 discloses the condensation of certain sugars, e.g., glucose, mannose, fructose, etc., with an aldehyde or ketone to form cyclic acetals of the sugar. The mechanism apparently involves the elimination of water by union of the oxygen of the carbonyl group of the aldehyde or ketone and the hydrogen from each of two hydroxyl groups of the sugar. This condensation reaction proceeds upon heating the mixture to the boiling point of the aldehyde in the presence of an acid acetalization catalyst, conditions favoring the open chain form of the sugar. The two adjacent carbon atoms of the cyclic acetal ring are adjacent carbons of the aliphatic chain of the sugar molecule. Several of such cyclic acetal rings may be formed on the same sugar molecule, forming poly-cyclic acetals.

OBJECTS OF THE INVENTION

An object of the present invention is to provide a process for preparing the novel compounds discussed herein.

Another object of this invention is to perform the reaction of the 2,3-dihydroxybutenolides and 2,5-dialkoxy-2,5-dihydrofurans of the invention in aqueous media.

Still another object of this invention is to provide novel compounds having immunomodulatory activity.

A still further object of the present invention is to provide novel compositions effective in the treatment of immune disorders, and methods for the application of such compositions.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed discussion.

The description of the novel invention described herein includes reference to the following figures:

FIG. 1 presents the X-ray crystal structure of the product of Example 1.

DESCRIPTION OF THE INVENTION

The novel compounds of the instant invention are produced by reacting approximately equal amounts of compound of the general formula ##STR1## wherein: R₁ and R₂ are selected from the group consisting of hydrogen and lower alkyl, provided that at least one is hydrogen;

R₃ and R₄ may be the same or different and are selected from the group consisting of lower alkyl and aryl;

R₅ and R₆ are selected from the group consisting of hydrogen and lower alkyl and may be the same or different

and a compound of the general formula ##STR2## wherein: X is selected from the group consisting of O, S, and NH;

R₇ and R₈ are selected from the group consisting of hydrogen and lower alkyl and may be the same or different;

R₇ may be ##STR3## R₉ is selected from the group consisting of ##STR4## R₁₀ and R₁₁ are selected from the group consisting of hydrogen, lower alkyl, phenyl and hydroxyl substituted lower alkyl and may be the same or different,

obtaining the product of the reaction, treating the product with acid anhydride or acid imide, refluxing and crystallizing the novel compounds. Recovery of the pure product may be facilitated by treatment or purification of the intermediate by any of the several techniques known to one of ordinary skill in the art such as, for example, charcoal filtration, ion exchange or gel chromatography.

The novel compounds produced by the above described process include ##STR5## wherein: R₂ is selected from the group consisting of hydrogen and lower alkyl;

R₅ and R₆ are selected from the group consisting of hydrogen and lower alkyl and may be the same or different;

R₇ and R₈ are selected from the group consisting of hydrogen and lower alkyl and may be the same or different;

R₇ may be ##STR6## R₉ is selected from the group consisting of ##STR7## R₁₀ and R₁₁ are selected from the group consisting of hydrogen, lower alkyl, phenyl and hydroxyl substituted lower alkyl and may be the same or different;

when R₇ contains a hydroxyl group in the α, β, or γ position, R₇ may form the hemiketal ring closure at carbon 3 of the butyrolactone with protonation of the carbonyl group on the same carbon atom;

n is selected from the group consisting of 1, 2, and 3; and

X is selected from the group consisting of O, S, and NH.

Lactone ring formation, ##STR8## wherein R₂, R₅, R₆, R₁₀, X, and n are as described above can occur. These rings will ordinarily partially rearrange, in aqueous or highly polar media to give tautomeric equilibrium products ##STR9## wherein R₂, R₅, R₆, R₇, R₈, R₁₀, R₁₁, and n are as described above.

The novel compounds can be formulated with generally known pharmaceutical carriers into compositions which can be administered to animals and humans. These compositions show immunomodulatory and cytotoxic activity at very low acute toxicity values.

It is believed that the cytotoxic activity of these compositions may be attributable to stimulation of the immune system by the compounds or to the cytoxicity of the compounds per se or to a combination of both effects.

The compositions may be used in immune therapy of depressed immune systems, as in the case of AIDS (Acquired Immune Disorder Syndrome).

The compositions, when administered to mammalian lymphocytes, have a profound effect on thier ability to reproduce as measured by their ability to synthesize DNA. This effect is bimodal. In higher concentrations, the compositions act as immunosuppressants while in lower concentrations they act as immunostimulants.

This immunomodulatory effect is seen in vitro in human blood lymphocytes and in vivo and in vitro in mouse spleen lymphocytes.

Various immunomodulatory studies have been conducted using these compositions. In these studies, T- and B-lymphocytes are isolated from human blood and mice spleens. Five strains of mice are used as lymphocyte donors, BALB/C, C57BL/6 BDF₁, SJL/J and DBA/2. The lymphocytes are then treated with plant proteins called lectins which act as mitogens.

Mitogens are substances which stimulate DNA synthesis and mitosis. The mitogens used in these studies were phytohemagglutinin (PHA) which is isolated from the red kidney bean and concanavalin-A (Con-A) which is isolated from the jack bean. Con-A binds to specific receptors (glycoproteins) containing -mannosyl or -glucosyl moieties and stimulates all murine T-cells to synthesize DNA, divide, and release lymphokines. Con-A in a soluble form allows distinction between T- and B-cells in the mouse, because although both T- and B-cells can bind 10⁶ molecules of Con-A per cell, only T-cells are stimulated when this lectin is presented in a soluble form. PHA stimulates only subpopulations (T₂ cells) of T- or B-cells. In the mouse, PHA activates a subpopulation of T-cells and does not stimulate B-cells. In humans, both T- and B-cells are probably stimulated. The activation of B-cells may be indirect and mediated by the release of soluble mediators from PHA-activated T-cells.

At doses ranging from 0.001 μg to 100 μg, the compounds of this invention have profound effects on lymphocyte mitogenesis when tested directly in vitro versus human lymphocytes. At lower doses, 0.001 to 1 μg, there is stimulation, above control levels, of PHA or Con-A mediated mitogenesis. At high doses, 10 to 100 μg, there is a profound suppression of the mitogenetic activity of lymphocytes treated with mitogens PHA and Con-A.

In vivo treatment of C57BL/6 mice comprising intraperitoneal (i.p.) administration of varying doses of the compounds for 4-12 days and subsequent testing of spleen lymphocytes with PHA and Con-A reveal a similar pattern to that of the in vitro system at doses of the compounds of 400 and 800 mg/kg versus 50 to 200 mg/kg. The observed suppression, at high doses, or stimulation, at low doses, showed statistically significant differences, with P<0.05.

Other experiments have been done to test the effect of the compounds on the antibody response to specific antigens, bovine serum albumin and keyhole limpet hemocyanin. It is found that high doses of the compounds do not inhibit the secondary immune response to the antigen but instead significantly enhance this response. Such doses, which routinely suppressed the in vivo and in vitro cell mediated response to mitogens did not significantly suppress humoral immunity. These data demonstrate the possibility of regulation of specific antibody production through immunostimulation.

In the experiments described below, the trends observed with high doses or low doses of the compound follow the general pattern noted above. However, differences can be noted in the actual response to the compounds of PHA versus Con-A stimulated lymphocytes. This may be due to the fact that Con-A and PHA do not stimulate the same kinds of lymphocytes. Differences can also be noted in the responses of the various strains of mice. These could reflect genetic variation with respect to response of lymphocytes to mitogens. Differences observed in the in vivo versus in vitro response can be due to differences in in vivo and in vitro metabolism and to the difference between the human and murine lymphocytes.

In all these experiments, it should be noted that control cultures not stimulated with mitogens or specific antigens, and which, therefore, could be considered resting cells, are not affected by the compounds. The dramatic stimulatory or inhibitory effects are only demonstrated in cells with active DNA synthesis, that is those cells undergoing cell division.

Tests were also done to determine the immunomodulatory effects of the compounds on the cytotoxic lymphocyte activity of sensitized lymphocytes obtained from tumor dormant DBA/2 mice. The experimental model involved establishment of the dormant state in DBA/2 mice and then conducting studies to assess the effect of the compounds disclosed in this invention on the tumor dormant state. The animal model described above, mimics a suspected tumor dormant state that is suggested by clinical observations of human recurrent breast tumors and melanomas many years after apparent cure of the primary tumors.

A. LYMPHOCYTE STIMULATION ASSAY PROTOCOLS

The purpose of this assay is to challenge lymphocytes in microcultures with one or more polyclonal mitogens at concentrations that will induce mitogenesis within 72 hours of stimulation.

In the mouse model, spleens are removed from different strains of mice and the spleen cells are teased free and suspended in RPMI-1640 tissue culture medium at a concentration of usually 1×10⁷ ml. These cells are dispensed at a concentration of 5.0×10⁵ cells per microculture well in a 96 well flat bottom 96 well tissue culture plate. All testing of the compounds of this invention or mitogens are done in replicates of 10. The cells are then treated with PHA, Con-A, specific antigens, or buffer only. If in vitro testing is done, varying concentrations of the compounds of this invention or buffer only are added to the cells as well. After treatment with the mitogens and/or compounds of this invention, the cells are incubated for 72 hours. The response of these cells to mitogens and/or the compounds of this invention is assessed using ¹⁴ C-thymidine labeling on the fourth day at a concentration of 0.01 μCi/well. The labeled cells are harvested using a lymphocyte harvestor and placed onto fibrous paper discs. A scintillation cocktail is added to vials contaning the discs and the results are obtained using a LKB-liquid scintillation counter (Model 1216/Rackbeta II). The data is expressed as a ratio of the cpm of the mitogen stimulated group to the control (non-mitogen) treated group=lymphocyte stimulation index (LSI).

The lymphocyte stimulation assay may be performed directly on spleen cells obtained from various strains of mice not treated with the compounds of this invention or on lymphocytes obtained from human plasma. In such experiments, the compounds of this invention are added directly to the spleen lymphocytes in vitro and the assay is completed and results interpreted. Alternatively, the mice may be treated in vivo with the compounds of this invention by intraperitoneal multi-dose schedules, followed by sacrifice and harvesting spleen lymphocytes. These cells are then tested for their response to polyclonal mitogens or specific antigens used to immunize the mice. In this sytem however, no additional compound is added to the in vitro lymphocyte stimulation assay system.

B. THE SECONDARY RESPONSE STUDIES

The effect of the compounds of this invention on the immune response to specific antigens involves immunization of mice with specific anitgens such as bovine serum albumin (BSA) or keyhole limpet hemocyanin (KLH). Following immunization, it is possible to assess the cell-mediated or humoral (antibody) immune response to these antigens by various methods:

(1) Lymphocyte stimulation assays can be performed using varying concentrations of the specific antigens as mitogens in the lymphocyte stimulation microculture system described above. The only difference is that the incubation period is extended to five days instead of three as for the polyclonal mitogens.

(2) Antibody response to soluble antigens such as BSA or KLH can be quantitated using a micro-ELISA solid phase heterogeneous immunoassay. The assay can be designed to quantitate class specific immunoglobulins (i.e., IgG or IgM).

Results of the humoral (antibody) response to BSA are obtained using a solid phase heterogeneous sandwich ELISA micromethod in 96 well Immulon microtiter plates. The cut-off for the titer was the highest dilution of mouse serum yielding an O.D.≦0.1 when read on the MR-600 Dynatech micro-ELISA reader.

C. MEASUREMENT OF CYTOTOXIC LYMPHOCYTE ACTIVITY--METHOD

A mixed lymphocyte tumor culture (MLTC) immunoassay, used to determine the cytotoxic lymphocyte (CTL) activity employs lymphocytes from either immunized (sensitized) mice or DBA/2 tumor dormant state animals in various stages of the tumor dormant state (TDS). The assay employs L5178Y target cells labeled with ⁵¹ Chromium and effector cells (sensitized lymphocytes) from the above-mentioned sources. Effector-target cell ratios will vary with different experimental conditions and may or may not include irradiated stimulator L5178Y cells. Results are expressed as % lysis of target cells based on ratio of cpm of test group over cpm of total release (maximum) both of which are corrected for spontaneous release of ⁵¹ Cr. The assay can be performed as an 8 or 18 hour release assay.

In order to induce the tumor dormant state (TDS), a large group of DBA/2 mice is injected subcutaneously with 1×10⁶ viable L5178Y leukemia cells subcutaneously on the midventral side of the abdomen. Ten days later the resultant tumor nodule, about 1 cm in size, is surgically excised. If the excision was successful, no subcutaneous tumors develop at the site of implantation. Seven days postexcision, the mice are challenged with 50,000 viable L5178Y leukemia cells, a dose that routinely produces death due to ascitic tumors in 100% of normal DBA/2 mice within 14 days. Immune mice resisted rapid outgrowth of the challenge L5178Y dose and remained clinically normal for many weeks thereafter. These mice are considered to be in the tumor dormant state.

ANTI-CANCER STUDIES--METHOD

Mice of the BDF₁ strain are given an i.p. inoculation of 10⁶ L-1210 leukemia cells on day 0. Twenty-four hours later, groups of 7 mice each are started on a nine day treatment regimen of various doses of the compounds of this invention. The experiment is continued according to the guidelines provided under the National Cancer Institute protocol for screening new anti-cancer agents and T/C ratios (median or mean survival time of treated groups over median or mean survival time of controls) are calculated. A T/C value ≧1.25 (or 125%) is considered significant anticancer activity.

EXAMPLE 1

93 g 2-methyl-2,5-dimethoxy-dihydrofuran (N. Clauson-Kaas and F. Lindborg (1947) Acta Chem. Scand. 1: 619. was added under vigorous mechanical stirring to a solution of 75 g L-ascorbic acid in 750 ml water at room temperature. The furan was used in 50% excess. The solution became homogenous within 15-20 minutes. The reaction was monitored by a high pressure liquid chromograph equipped with a UV detector. The original peak of Rf 1.6 of L-ascorbic acid at 254 nm in 20% aqueous methanol disappeared while a new peak appeared at Rf 5.9 to 6.0, under 64 atmospheres. It was simultaneously observed that the solution did not consume any more iodine which is indicative of the total disappearance of L-ascorbic acid.

After standing overnight at 20° C. the aqueous solution was freeze-dried to give a pale yellow foam. The latter showed well defined IR, ¹³ C NMR and ¹ H NMR spectra.

Next, 64.0 g (0.25M) of the crude product (melting point 55° C.) and 25.0 g (0.25M) of succinic anhydride were placed into a 1 liter round-bottomed flask equipped with a reflux condenser and a nitrogen inlet tube. After adding 200 ml of HPLC-grade ethyl acetate, the reaction mixture was refluxed for 4 hours. The homogeneous solution was cooled to room temperature and then placed in an ice-water bath. A white precipitate formed which was filtered by suction and washed with a few ml of cold ethyl acetate to give 29.9 g of the crude product (yield 46.6%). The filtrate was concentrated to half volume and cooled in an ice-water bath. The second crop of precipitate was again filtered to give 13.5 g of solid which contained some unreacted succinic anhydride.

The product was recrystallized from a solvent mixture (ethyl acetate/chloroform : 20/80) to give a total yield of 22.5 g (yield 35.2%) of pure product (long white needles--melting point 134°-134.5° C.).

Analysis: Calculated for C₂₆ H₂₈ O₁₇ : C, 50.99; H, 4.61; O, 44.41.

Found: C, 50.67; H, 4.52; O, 44.58.

X-ray crystallography, FIG. 1, confirmed the structure of the compound and showed the presence of a 2:1, 2-furylbutyrolactone:succinic anhydride, molecular complex in a unit cell. ##STR10##

EXAMPLE 2

186 g 2-methyl-2,5-dimethoxy-dihydrofuran (N. Clauson-Kaas and F. Lindborg (1947) Acta Chem. Scand. 1: 619. was added under vigorous mechanical stirring to a solution of 150 g L-ascorbic acid in 1.5 L water at room temperature. The furan was used in 50% excess. The solution became homogenous within 15-20 minutes. The reaction was monitored by a high pressure liquid chromograph equipped with a UV detector. The original peak of Rf 1.6 of L-ascorbic acid at 254 nm in 20% aqueous methanol disappeared while a new peak appeared at Rf 5.9 to 6.0, under 64 atmospheres. It was simultaneously observed that the solution did not consume any more iodine which is indicative of the total disappearance of L-ascorbic acid.

After standing overnight at 20° C. the aqueous solution was freeze-dried to give a pale yellow foam. The latter showed well defined IR, ¹³ C NMR and ¹ H NMR spectra.

Next, 119.65 g (0.467 mole--assuming 100% purity) of the crude product (melting point 55° C.) were dissolved in 216 ml of HPLC grade ethylacetate. 23.3 g succinimide (0.235 mole) were added and the mixture was stirred under positive nitrogen pressure. After a few minutes of stirring, a white solid precipitated. The reaction mixture was then heated for 30 min. in an oil bath until the solid redissolved. Heating was stopped and the solution was allowed to cool to room temperature while stirring and then in an ice water bath for 2 hours. A precipitate formed which was filtered by suction, washed with 150 ml of cold chloroform and dried under vacuum to give 67.4 g of crude product (56.3% yield).

The product was recrystallized from a solvent mixture (ethyl acetate/chloroform : 60/40) to give a total yield of 52.2 g (yield 43.6%) of pure product (long white needles--melting point 132°-133° C.).

Analysis: Calculated for C₂₆ H₂₉ NO₁₆ : C, 51.07; H, 4.78; O, 41.86; N, 2.29.

Found: C, 51.17; H, 4,93; O, 41.81; N, 2.21.

X-ray crystallography, confirmed the structure of the compound and showed the presence of a 2:1, 2-furylbutyrolactone:succinimide molecular complex in a unit cell. ##STR11##

EXAMPLE 3

93 g 2-methyl-2,5-dimethoxy-dihydrofuran (N. Clauson-Kaas and F. Lindborg (1947) Acta Chem. Scand. 1: 619. was added under vigorous mechanical stirring to a solution of 75 g L-ascorbic acid in 750 ml water at room temperature. The furan was used in 50% excess. The solution became homogenous within 15-20 minutes. The reaction was monitored by a high pressure liquid chromograph equipped with a UV detector. The original peak of Rf 1.6 of L-ascorbic acid at 254 nm in 20% aqueous methanol disappeared while a new peak appeared at Rf 5.9 to 6.0, under 64 atmospheres. It was simultaneously observed that the solution did not consume any more iodine which is indicative of the total disappearance of L-ascorbic acid.

After standing overnight at 20° C. the aqueous solution was freeze-dried to give a pale yellow foam. The latter showed well defined IR, ¹³ C NMR and ¹ H NMR spectra.

Next, 10.24 g (0.04M) of the crude product (melting point 55° C.) and 2.5 g (0.022M) of N-methylsuccinimide were placed into a 1 liter round-bottomed flask equipped with a reflux condenser and a nitrogen inlet tube. After adding 20 ml of HPLC-grade ethyl acetate, the reaction mixture was refluxed for 4 hours. The homogeneous solution was cooled to room temperature and then placed in an ice-water bath. A white precipitated formed which was filtered by suction and washed with a few ml of cold ethyl acetate to give 5.20 g of the crude point (yield 50.8%). The filtrate was concentrated to half volume and cooled in an ice-water bath.

The product was recrystallized from a solvent mixture (ethyl acetate/chloroform : 1/1) to give a total yield of 3.21 g (yield 31.3%) of pure product (long white needles--melting point 105°-106.5° C.).

Analysis: Calculated for C₂₇ H₃₁ NO₁₆ : C, 51.84; H, 5.00; N, 2.24; O, 40.92.

Found: C, 51.98; H, 5.12; N, 2.08; O 40.63.

X-ray crystallography, FIG. 1, confirmed the structure of the compound and showed the presence of a 2:1, 2-furylbutyrolactone:N-methylsuccinimide molecular complex in a unit cell. ##STR12##

EXAMPLE 4

The compound of Example 1 dissolves completely in 0.238 molar bicarbonate buffered saline (0.85%) to form ##STR13## and succinic anhydride.

EXAMPLE 5

The compound of Example 2 dissolves completely in 2.38 mm bicarbonate buffered saline (0.89%) to form ##STR14## and succinimide.

EXAMPLE 6

The compound of Example 3 dissolves completely in 2.38 mm bicarbonate buffered saline (0.85%) to form ##STR15## and N-methylsuccinimide.

EXAMPLE 7

Single dose LD₅₀ in C57BL/6 mice for Cpd. 1 is determined following the method of Spearman and Karber described in Basic Exercises in Immunochemistry, 1979. Briefly, 0.5 ml of each dose is given to each of ten mice. The survivors are counted after 3 days and the LD₅₀ is calculated using the following formula: ##EQU1## where D=fold diferences between doses, R=total number dead, and N=total number of animals tested.

                  TABLE 1                                                          ______________________________________                                         Results of Cpd. 1 Single I.P. Dose LD.sub.50 Determination                     Using C57BL/6 Strain of Mice                                                   Dose of Cpd. 1     Number Dead on Day 3                                        ______________________________________                                         272 mg/17 g mouse (16,000 mg/kg)                                                                  10                                                          136 mg/17 g mouse (8,000 mg/kg)                                                                   10                                                           68 mg/17 g mouse (4,000 mg/kg)                                                                   7                                                            34 mg/17 g mouse (2,000 mg/kg)                                                                   0                                                            17 mg/17 g mouse (1,000 mg/kg)                                                                   0                                                           ______________________________________                                    

Cpd. 1 LD₅₀ =59.2 mg/17 g mouse=3,480 mg/kg.

Purified Cpd. 1 is tested in C57BL/6 mice by single i.p. injection and gives an LD₅₀ in excess of 3 g/kg.

EXAMPLE 8

Single oral dose LD₅₀ in CD-1 mice and CD rats, obtained from Charles River U.K. Ltd., for Cpd. 1 is determined. Briefly, the compound, 5 g/kg, is dissolved in 0.0238M bicarbonate buffer containing 0.85% sodium chloride, pH 6.8, and administered orally using a constant dose volume of 10 ml/kg. Cpd. 1, dissolved in buffer, or just buffer is administered orally and the mice and rats are observed for 14 days after dosing. After 14 days, the animals are sacrified and necropsy is performed to check for gross evidence of toxicity.

No deaths or signs of toxicity are observed during this study, indicating a single oral dose LD₅₀ for Cpd. 1 in excess of 5 g/kg.

EXAMPLE 9

Two strains of mice, C57BL/6 and BDF₁ are treated for seven days with i.p. administration of either 25, 50, 100, 200, or 400 mg/kg of Cpd. 1 or just buffer. This is followed on the eighth day by a lymphocyte stimulation assay.

                  TABLE 2-A                                                        ______________________________________                                         Effect of Cpd. 1 In Vivo, as Measured by the Lymphocyte                        Stimulation Assay, on C57BL/6 Strain of Mice                                            Lymphocyte Stimulation Index                                          Cpd. 1 Conc.                                                                              PHA        Con-A    Control                                         ______________________________________                                         400 mg/kg   3.2       20.7     1.0                                             200 mg/kg  21.3       34.0     1.0                                             100 mg/kg  17.7       40.0     1.3                                              50 mg/kg  *          26.0     1.0                                              0 mg/kg   17.3       16.7     --                                              ______________________________________                                          *No results reported                                                     

                  TABLE 2-B                                                        ______________________________________                                         Effect of Cpd. 1 In Vivo, as Measured by the Lymphocyte                        Stimulation Assay, on BDF.sub.1 Strain of Mice                                          Lymphocyte Stimulation Index                                          Cpd. 1 Con.                                                                               PHA        Con-A    Control*                                        ______________________________________                                         400 mg/kg  1.1        0.9      0.9                                             200 mg/kg  7.8        2.9      0.8                                             100 mg/kg  48.7       17.9     0.7                                              50 mg/kg  52.1       21.6     0.9                                              25 mg/kg  13.8       4.3      0.8                                              0 mg/kg   5.5        1.6      --                                              ______________________________________                                          *Buffer, pH 8.05                                                         

The high dose of 400 mg/kg shows strong suppression of the PHA response in the C57BL/6 mice as well as BDF₁ mice, a slight suppression of the Con-A response in the BDF₁ mice, and a suppression of the Con-A response in C57BL/6 mice when compared to the 200 mg/kg dose. However, the stimulation of T-lymphocyte proliferation is evident for PHA at doses of 50 and 100 mg/kg in BDF₁ mice and at a dose of 200 mg/kg in C57BL/6 mice. The Con-A response in the BDF₁ strain is significantly increased at doses between 50 and 100 mg/kg of Cpd. 1 and in the C57BL/6 strain, it is increased at doses of 50, 100 and 200 mg/kg.

EXAMPLE 10

A comparison is made of the lymphocyte response to C57BL/6 mice treated 4 days with i.p. administration of either 50, 100, 200, 400 or 800 mg/kg of Cpd. 1, 50, 100, 200, 400 or 800 mg/kg of ascorbic acid (AA), or just buffer. This is followed on the fifth day by a lymphocyte stimulation assay.

                  TABLE 3-A                                                        ______________________________________                                         Effect of AA In Vivo, as measured by the Lymphocyte                            Stimulation Assay, in C57BL/6 Strain of Mice                                           Lymphocyte Stimulation Index                                           AA Conc.  PHA         Con-A    Control                                         ______________________________________                                         800 mg/kg 12.1        23.9     .50                                             400 mg/kg 14.3        17.8     1.3                                             200 mg/kg 10.0        21.1     1.3                                             100 mg/kg 17.1        19.8     1.8                                              50 mg/kg 17.1        25.5     .56                                              0 mg/kg  14.2        17.1     --                                              ______________________________________                                    

                  TABLE 3-B                                                        ______________________________________                                         Effect of Cpd. 1 In Vivo, as Measured by the Lymphocyte                        Stimulation Assay, in C57BL/6 Strain of Mice                                            Lymphocyte Stimulation Index                                          Cpd. 1 Conc.                                                                              PHA        Con-A    Control                                         ______________________________________                                         800 mg/kg  .408       .612     .31                                             400 mg/kg  4.8        40.0     1.0                                             200 mg/kg  42.8       67.4     1.6                                             100 mg/kg  34.8       80.0     1.6                                              50 mg/kg  *          52.8     1.2                                              0 mg/kg   33.0       32.6     --                                              ______________________________________                                          *No results reported.                                                    

No statistically significant measurable effect of AA was demonstrable with PHA but a single stimulation of proliferation did occur at 50 mg/kg in the Con-A stimulated group.

In spleen cells treated with PHA, doses of 100 and 200 mg/kg of Cpd. 1 tend to stimulate lymphocyte DNA synthesis. Doses ranging from 400 to 800 suppress DNA synthesis of spleen lymphocytes. In spleen cells treated with Con-A, doses ranging from 50 to 200 mg/kg have a significant stimulatory effect and doses ranging from 400 to 800 mg/kg have a significant anti-proliferative effect, particularly the 800 mg/kg dose. These data suggest an immunostimulatory effect of Cpd. 1 at low to median concentrations and an immunosuppressive effect of Cpd. 1 at higher concentrations. Also, the likelihood that ascorbic acid by itself can exert a similar effect to Cpd. 1 is unsupported by these experiments.

EXAMPLE 11

Two strains of mice, C57BL/6 and BALB/c, are treated 4 days with i.p. administration of either 50, 100, 200, or 400 mg/kg of Cpd. 1, or just buffer. This is followed on the fifth day by a lymphocyte stimulation assay.

                  TABLE 4-A                                                        ______________________________________                                         Effect of Cpd. 1 In Vivo, as Measured by the Lymphocyte                        Stimulation Assay, in C57BL/6 Strain of Mice                                            Lymphocyte Stimulation Index                                          Cpd. 1 Conc.                                                                              PHA        Con-A    Control                                         ______________________________________                                         400 mg/kg  14.8       30.9     .61                                             200 mg/kg  25.2       41.1     .93                                             100 mg/kg  17.0       22.3     1.3                                              50 mg/kg  13.6       20.6     .87                                              0 mg/kg    7.85      11.4     --                                              ______________________________________                                    

                  TABLE 4-B                                                        ______________________________________                                         Effect of Cpd. 1 In Vivo, as Measured by the Lymphocyte                        Stimulation Assay, in BALB/C Strain of Mice                                             Lymphocyte Stimulation Index                                          Cpd. 1 Conc.                                                                              PHA        Con-A    Control                                         ______________________________________                                         400 mg/kg  6.71       18.7      .90                                            200 mg/kg  7.65       20.5      .76                                            100 mg/kg  5.24       21.8     1.0                                              50 mg/kg  6.44       20.5     1.4                                              0 mg/kg   1.76        9.87    --                                              ______________________________________                                    

In spleens treated with PHA and Con-A, doses of 50, 100 and 200 mg/kg tend to stimulate lymphocyte DNA synthesis in both strains of mice. Doses of 400 mg/kg suppress DNA synthesis of spleen cell lymphocytes when compared to the activity at a dose of 200 mg/kg.

EXAMPLE 12

An in vitro lymphocyte stimulation assay is performed directly on normal spleen lymphocytes removed from five normal C57BL/6 mice, using concentrations of Cpd. 1 of 0.001, 0.01, 0.1, 1.0, or 10 μg test well (5×10⁵ cells/well) or just buffer. Following three days of incubation the assay is completed.

                  TABLE 5-A                                                        ______________________________________                                         Effect of Cpd. 1 In Vitro, as Measured by the Lymphocyte                       Stimulation Assay, in C57BL/6 Strain of Mice                                             Lymphocyte Stimulation Index                                         Cpd. 1 Conc.                                                                               PHA        Con-A    Control                                        ______________________________________                                         10     μg/well                                                                              .920       2.15   1.9                                          1      μg/well                                                                              53.8       178    2.6                                          .1     μg/well                                                                              83.1       198    3.2                                          .01    μg/well                                                                              87.5       198    3.2                                          .001   μg/well                                                                              80.4       198    3.8                                          0      μg/well                                                                              21.9       126    --                                           ______________________________________                                    

The results indicate significant stimulation of mitogenesis across a range of doses from 0.001-1.0 μg/well and significant suppression at a dose of 10 μg/well for both PHA and Con-A mitogens. The range of concentration effectiveness in vitro may be the result of exclusion of the influence of the host's metabolic system on drug metabolism.

EXAMPLE 13

Lymphocytes isolated from 5 human volunteers are treated in vitro with PHA and Con-A and either 0.1, 1, 10, 50, or 100 μg/well of Cpd. 1, 0.1, 1, 10, 50, or 100 μg/well of AA, or buffer.

                  TABLE 6-A                                                        ______________________________________                                         Effect of AA on the In Vitro Lymphocyte                                        Stimulation Assay in Humans                                                                 Lymphocyte Stimulation Index                                      AA Concentration                                                                              PHA        Con-A                                                ______________________________________                                         100     μg/well 34.23      25.18                                            50      μg/well 35.93      23.31                                            10      μg/well 35.10      27.35                                            1.0     μg/well 34.69      24.76                                            0.1     μg/well 38.29      24.37                                            0       μg/well 31.25      25.86                                            ______________________________________                                    

                  TABLE 6-B                                                        ______________________________________                                         Effect of Cpd. 1 on the In Vitro Lymphocyte                                    Stimulation Assay in Humans                                                                  Lymphocyte Stimulation Index                                     Cpd. 1 Concentration                                                                           PHA        Con-A                                               ______________________________________                                         100     μg/well  0.544      0.44                                            50      μg/well  0.40       1.33                                            10      μg/well  34.37      23.82                                           1.0     μg/well  48.60      32.63                                           0.1     μg/well  56.67      38.06                                           0       μg/well  39.82      26.62                                           ______________________________________                                    

There is no significant proliferative or anti-proliferative effect demonstrated for AA alone. Whereas for Cpd. 1, a high dose anti-proliferative effect, at doses of 100 and 50 μg/ml, is followed by a markedly increased lymphocyte response at very low doses of 1 and 0.1 μg/ml. The same profile of results are exhibited for both PHA and Con-A mitogens.

EXAMPLE 14

C57BL/6 mice were treated with four daily i.p. doses of either 50, 100, 200, or 400 mg/kg of Cpd. 1 or just buffer. On the fifth day a lymphocyte stimulation assay was performed.

                  TABLE 7                                                          ______________________________________                                         Effect of Cpd. 1 In Vivo, as Measured by the Lymphocyte                        Stimulation Assay, in C57BL/6 Strain of Mice                                            Lymphocyte Stimulation Index                                          Cpd. 1 Conc.                                                                              PHA        Con-A    Control                                         ______________________________________                                         400 mg/kg  18.7       26.4     .31                                             200 mg/kg  23.2       26.3     .22                                             100 mg/kg  23.8       25.4     .40                                              50 mg/kg  17.0       23.0     1.1                                              0 mg/kg   14.9       19.9     --                                              ______________________________________                                    

Stimulation of the response to polyclonal mitogens at doses of Cpd. 1 from 50-400 mg/kg with a maximum response achieved between doses of 100-200 mg/kg for both PHA and Con-A test mitogens was observed. It can also be seen that there was a decrease in the response to PHA at the 400 mg/kg dose when compared to the response at the 200 mg/kg dose. This appears to follow the trend of immunosuppression at high doses.

EXAMPLE 15

The in vivo immunomodulatory effect of Cpd. 1 on C57BL/6 mice was studied.

Mice of the C57BL/6 strain were tested with i.p. administration of either 100, 200, 400 or 600 mg/kg of Cpd. 1 or just buffer. This was followed by removal of spleens and treatment of lymphocytes therein with mitogens PHA and Con-A.

                  TABLE 8                                                          ______________________________________                                         Effect of Cpd. 1 In Vivo, as Measured by the Lymphocyte                        Stimulation Assay, on C57BL/6 Strain of Mice                                            Lymphocyte Stimulation Index                                          Cpd. 1 Conc.                                                                              PHA        Con-A    Control                                         ______________________________________                                         600 mg/kg  17.6       26.5     1.7                                             400 mg/kg  44.9       42.4     .49                                             200 mg/kg  48.2       36.6     .62                                             100 mg/kg  51.1       43.9     .80                                              0 mg/kg   13.1       26.7     --                                              ______________________________________                                    

Doses ranging from 100 to 400 mg/kg of Cpd. 1 caused significant stimulation of both the Con-A and PHA treated lymphocytes. The high dose, 600 mg/kg, caused less stimulation than the 100 to 400 mg/kg doses and gave levels comparable to controls. There was no evidence of toxicity in the 600 mg/kg treated animals given the five day administration of Cpd. 1.

EXAMPLE 16

An in vitro lymphocyte stimulation assay was performed using spleen lymphocytes from normal C57BL/6 mice. The lymphocytes were treated with either 1, 5, 10, 50, or 100 μg/well of Cpd. 1 or buffer.

                  TABLE 9                                                          ______________________________________                                         Effect of Cpd. 1 In Vitro, as Measured by the Lymphocyte                       Stimulation Assay, in C57BL/6 Strain of Mice                                             Lymphocyte Stimulation Index                                         Cpd. 1 Conc.                                                                               PHA        Con-A    Control                                        ______________________________________                                         100    μg/well                                                                              .292       .308   .20                                          50     μg/well                                                                              .261       3.78   .20                                          10     μg/well                                                                              126        194    .66                                          5      μg/well                                                                              157        162    1.8                                          1      μg/well                                                                              80.4       123    1.2                                          0      μg/well                                                                              59.5       122    --                                           ______________________________________                                    

Doses of 5 and 10 μg/well caused significant increases in the response to PHA and Con-A while doses of 50 and 100 μg/well caused significant decreases in the lymphocyte response to the mitogens.

EXAMPLE 17

The compound of Example 2, Cpd. 2, was tested in vivo by using C57BL/6 mice and treating them with Cpd. 3 or just buffer for four consecutive days by the i.p. route. On the fifth day a lymphocyte stimulation assay was performed.

                  TABLE 3-B                                                        ______________________________________                                         Effect of Cpd. 2 In Vivo, as Measured by the Lymphocyte                        Stimulation Assay, in C57BL/6 Strain of Mice                                            Lymphocyte Stimulation Index                                          Cpd. 2 Conc.                                                                              PHA        Con-A    Control                                         ______________________________________                                         600 mg/kg  15.8       94.0     1.5                                             400 mg/kg  12.9       109      1.3                                             200 mg/kg  11.3       99.3     .69                                             100 mg/kg  15.4       105      1.5                                              50 mg/kg  15.5       96.1     .88                                              0 mg/kg   11.0       75.1     --                                              ______________________________________                                    

Cpd. 2 produced only marginal stimulation of Con-A mitogenesis and had no effect on PHA mitogenesis.

EXAMPLE 18

Cpd. 2 was tested using normal spleen lymphocytes from C57BL/6 mice. A lymphocyte stimulation assay was conducted using either 1, 5, 10, 50, or 100 μg/well Cpd. 3 or just buffer.

                  TABLE 11                                                         ______________________________________                                         Effect of Cpd. 2 In Vitro, as Measured by the Lymphocyte                       Stimulation Assay, in C57BL/6 Strain of Mice                                             Lymphocyte Stimulation Index                                         Cpd. 2 Conc.                                                                               PHA        Con-A    Control                                        ______________________________________                                         100    μg/well                                                                               3.83      144    .49                                          50     μg/well                                                                              45.8       218    .80                                          10     μg/well                                                                              38.8       164    1.1                                          5      μg/well                                                                              29.8       148    1.2                                          1      μg/well                                                                              25.4       147    .92                                          0      μg/well                                                                              23.5       175    --                                           ______________________________________                                    

In spleen cells treated with PHA, doses of 50 and 100 μg/well of Cpd. 2 tended to stimulate lymphocyte DNA synthesis. The 100 μg/well dose suppressed DNA synthesis of spleen lymphocytes. In spleen cells treated with Con-A, the 200 μg/well dose had a stimulatory effect and the 400 μg/well doses had an anti-proliferative effect.

EXAMPLE 19

Spleen cells from C57BL/6 mice were treated, in vitro, with the crystallizing reagents, succinic acid and succinimide. Since these compounds are spontaneously released from the molecular complex in solution at a molar ratio of 2 moles of Cpds. 1, 2, or 3 per mole of the crystalline reagent, these reagents were treated in the lymphocyte stimulation assay at proper molar concentrations.

                  TABLE 12-A                                                       ______________________________________                                         Effect of Succinic Acid In Vitro, as Measured                                  by the Lymphocyte Stimulation Assay, in                                        C57BL/6 Strain of Mice                                                                     Lymphocyte Stimulation Index                                       Succinic Acid Conc.                                                                          PHA       Con-A    Control                                       ______________________________________                                         16.6    μg/well                                                                               11.5      38.5   1.1                                         8.3     μg/well                                                                               12.4      35.6   .91                                         4.15    μg/well                                                                               14.0      42.3   .91                                         2.08    μg/well                                                                               15.3      51.1   1.0                                         1.04    μg/well                                                                               15.7      64.6   .94                                         0       μg/well                                                                               15.9      83.5   --                                          ______________________________________                                    

                  TABLE 12-B                                                       ______________________________________                                         Effect of Succinimide In Vitro, as Measured                                    by the Lymphocyte Stimulation Assay,                                           in C57BL/6 Strain of Mice                                                                  Lymphocyte Stimulation Index                                       Succinimide Acid Conc.                                                                       PHA       Con-A    Control                                       ______________________________________                                         13.92  μg/well 17.1      92.9   1.4                                         6.96   μg/well 17.2      71.9   1.1                                         3.48   μg/well 18.1      85.1    .98                                        1.74   μg/well 17.5      83.4   1.1                                         0.87   μg/well 19.5      76.0    .91                                        0      μg/well 19.1      100    --                                          ______________________________________                                    

The lymphocytes treated with succinic acid showed a decrease in PHA and Con-A mitogenesis with increased succinic acid dosage. The succinimide demonstrated no significant suppressive or enhancing effect on the response of the lymphocytes to either mitogen.

EXAMPLE 20

The compound of example 3, Cpd. 3, was used to treat C57BL/6 spleen lymphocytes in vitro. The lymphocytes were treated with either 1, 5, 10, 50, or 100 μg/well of Cpd. 3 or just buffer and then a lymphocyte stimulation assay was performed.

                  TABLE 13                                                         ______________________________________                                         Effect of Cpd. 3 In Vitro, as Measured by the Lymphocyte                       Stimulation Assay, in C57BL/6 Strain of Mice                                             Lymphocyte Stimulation Index                                         Cpd. 3 Conc.                                                                               PHA        Con-A    Control                                        ______________________________________                                         100    μg/well                                                                              0.263       2.88  .25                                          50     μg/well                                                                              4.08       97.2   .27                                          10     μg/well                                                                              24.0       89.6   .47                                          5      μg/well                                                                              18.5       80.9   .64                                          1      μg/well                                                                              12.5       73.2   .60                                          0      μg/well                                                                              12.2       94.6   --                                           ______________________________________                                    

The 10 μg/well dose of Cpd. 3 significantly stimulated the response to PHA while the 50 and 100 μg/well doses suppressed the response. The 50 μg/well dose slightly stimulated the response to Con-A and the 100 μg/well dose suppressed the response.

EXAMPLE 21

Three month old mice of the SJL/J strain, which are T-cell deficient, are treated with i.p. administration of 100, 200, or 400 mg/kg of Cpd. 1 or just buffer for four days. This is followed by a lymphocyte stimulation assay.

                  TABLE 14                                                         ______________________________________                                         Effect of Cpd. 1 In Vivo, as Measured by the Lymphocyte                        Stimulation Assay, in SJL/J Strain of Mice                                              Lymphocyte Stimulation Index                                          Cpd. 1 Conc.                                                                              PHA        Con-A    Control                                         ______________________________________                                         400 mg/kg  2.31       3.30     0.693                                           200 mg/kg  1.79       4.57     0.732                                           100 mg/kg  1.85       5.01     0.573                                            0 mg/kg   1.11       2.4      --                                              ______________________________________                                    

EXAMPLE 22

The SJL/J mice apparently shift to a loss of immune regulation function as they age and the latter is evidenced by a hyperresponsiveness to alloantigens and production of circulating antibodies to nuclear material as well as synthetic double stranded RNA and poly I/C. The continuous erosion of immune competence in the SJL/J mice has been observed to extend from birth to death indicating defects in regulatory T-cell subpopulations (possibly suppressor and/or amplifier cells). Because the dynamics of the T-lymphocyte population changes with age, it must be assumed that age plays a role in affecting the results obtained when treating SJL/J mice with Cpd. 1.

An in vivo lymphocyte stimulation assay was performed on SJL/J mice of different ages, either 2, 5, or 10 months. The mice received i.p. injections of either 100 mg/kg of Cpd. 1 or just buffer.

                  TABLE 15                                                         ______________________________________                                         Effect of Cpd. 1 In Vivo, as Measured by the Lymphocyte                        Stimulation Assay, in SJL/J Strain of Mice                                                Lymphocyte Stimulation Index                                        Age of Mice (Months)                                                                        PHA        Con-A    Control                                       ______________________________________                                         2     0 mg/kg    40.8       103    --                                               100 mg/kg   32.6       167    2.3                                         5     0 mg/kg    2.09       19.5   --                                               100 mg/kg   1.16       12.9   1.9                                         10    0 mg/kg    3.97       21.9   --                                               100 mg/kg   9.18       14.5   2.1                                         ______________________________________                                    

The results obtained from the untreated controls demonstrated the age dependent variation of the PHA and Con-A lymphocyte proliferation responses.

Also, at 2 months of age Cpd. 1 administered at a dose of 100 mg/kg caused a decreased PHA versus increased Con-A response. In contrast, at 5 months of age the SJL/J mice given the dose of Cpd. 1 showed a depressed mitogenesis response to both PHA and Con-A. The ten month old SJL/J mice showed a complete reversal and demonstrated significant stimulation of both the PHA and Con-A mitogenic response upon treatment of mice at the same dose.

EXAMPLE 23

Mice of the C57BL/6 strain are given i.p. injections of either 50, 100, 200 or 400 mg/kg of Cpd. 1 or buffer for twelve days (days 1-12). An antigen, bovine serum albumin (BSA), is administered intraperitoneally with Freund's Complete Adjuvant (FCA) on days 1, 7 and 14. Blood samples are taken for assay of the antibody response on days 0, 5, 13, and 19. Also, on days 13 and 10 a lymphocyte proliferation assay is performed on spleen lymphocytes from these same mice using either the BSA antigen as the specific recall antigen (mitogen) at concentrations of 0.01, 0.1, 0.5 or 1.0 μg/well or just buffer.

                  TABLE 16-A                                                       ______________________________________                                         Enhancement of the Secondary Immune Response to                                BSA by Cpd. 1, as Measured by Micro-ELISA titer                                              Micro-ELISA Titer                                                Cpd. 1 Conc.                                                                              Prebleed Day 5      Day 13                                                                               Day 19                                    ______________________________________                                         400 mg/kg   N/R*    N/R        1:80  1:320                                     200 mg/kg  N/R      N/R        1:80   1:1280                                   100 mg/kg  N/R      N/R        1:40   1:1280                                    50 mg/kg  N/R      N/R        1:40  1:640                                      0 mg/kg   N/R      N/R        1:20  1:320                                     ______________________________________                                          *N/R = no response.                                                      

                  TABLE 16-B                                                       ______________________________________                                         Effect of Cpd. 1 In Vivo on the Secondary Immune Response                      to BSA, as Measured by Lymphocyte Stimulation                                  Assay, in C57BL/6 Strain of Mice, Day 13                                                Lymphocyte Stimulation Index                                                   BSA (μg/well)                                                      Cpd. 1 Conc.                                                                              0         0.01   0.1    0.5  1                                      ______________________________________                                         400 mg/kg  10.9      13.7   12.8   12.3 13.8                                   200 mg/kg  10.6      14.1   15.8   13.8 14.0                                   100 mg/kg   3.22      9.8   11.9   12.3 10.2                                    50 mg/kg  16.5      19.9   23.1   22.9 18.2                                    0 mg/kg   --        14.0   14.6   12.8 13.0                                   ______________________________________                                    

                  TABLE 16-C                                                       ______________________________________                                         Effect of Cpd. 1 In Vivo on the Secondary Immune Response                      to BSA, as Measured by Lymphocyte Stimulation                                  Assay, in C57BL/6 Strain of Mice, Day 19                                                Lymphocyte Stimulation Index                                                   BSA (μg/well)                                                      Cpd. 1 Conc.                                                                              0        0.01   0.1     0.5  1.0                                    ______________________________________                                         400 mg/kg  5.0      3.26   2.89    1.94 1.04                                   200 mg/kg  0.42     2.94   2.82    2.56 2.12                                   100 mg/kg  4.1      3.79   2.68    2.03  .26                                    50 mg/kg  .26      2.33   2.27    2.37 2.63                                    0 mg/kg   --       1.58   1.56    2.07 1.02                                   ______________________________________                                    

No antibody response is observed until day 13. On that day, a significant (four-fold) stimulation is observed at Cpd. 1 doses of 200 and 400 mg/kg and only a slight amount of stimulation is observed at doses of 50 and 100 mg/kg of Cpd. 1. A much more dramatic response is observed on day 19. At that time, the antibody responses to BSA are equal at the 0 mg/kg and 400 mg/kg dose of Cpd. 1, and higher than observed on day 13. A slight increase of antibody titer over the control is observed at 50 mg/kg of Cpd. 1 while 100 and 200 mg/kg doses of Cpd. 1 are extremely stimulatory, demonstrating a 16-fold increase over controls.

The second component of Example 23 illustrates the effects of Cpd. 1 on the lymphocyte proliferation of spleen cells to the immunizing antigen (BSA). Only the 50 mg/kg dose shows significant stimulation of DNA synthesis on day 13 compared to controls. This effect has waned by day 19, indicating the importance of sustaining treatment to stimulate the cell-mediated (T-cell) component of the immune response. The above mentioned antibody response is likely to be sustained after cessation of therapy since the half life of IgG (the antibody) in vivo is approximately 5-7 days.

EXAMPLE 24

Mice of the C57BL/6 strain are given i.p. injections of either 50, 100, 200 or 400 mg/kg of Cpd. 1 or buffer for ten days (days 1-10). An antigen, keyhole limpet hemocyanin (KLH), is administered intraperitoneally with Freund's Complete Adjuvant (FCA) on days 1, 7, and 13. Blood samples are taken for assay of the antibody response on days 0, 5, 12, and 17. Spleens are removed, lymphocytes isolated and a lymphocyte stimulation assay with PHA, Con-A or KLH antigen as the mitogens is performed on day 17 of the experiment.

                  TABLE 17-A                                                       ______________________________________                                         Enhancement of the Secondary Immune Response to KLH                            by Cpd. 1, as Measured by Micro-ELISA Titer                                                  Micro-ELISA Titer                                                Cpd. 1 Conc.                                                                              Prebleed Day 5     Day 12                                                                               Day 17                                     ______________________________________                                         400 mg/kg   N/R*    N/R       1:5120                                                                                 1:10,240                                 200 mg/kg  N/R      N/R       1:5120                                                                                 1:10,240                                 100 mg/kg  N/R      N/R       1:2560                                                                               1:5120                                      50 mg/kg  N/R      N/R       1:2560                                                                               1:5120                                      0 mg/kg   N/R      N/R       1:2560                                                                               1:1280                                     ______________________________________                                          *N/R -- no response.                                                     

                  TABLE 17-B                                                       ______________________________________                                         Effect of Cpd. 1 In Vivo on the Response to KLH, PHA and                       Con-A as Measured by Lymphocyte Stimulation Assay,                             in C57BL/6 Strain of Mice, Day 17                                                    Lymphocyte Stimulation Index                                             Cpd. 1                                                                               KLH (μg/well)                                                         Conc. 1.0    0.5    0.5  0.025  PHA   Con-A Control                            ______________________________________                                         400   0.589  0.232  0.667                                                                               1.03   2.32  35.5  0.840                              mg/kg                                                                          200   7.45   4.26   1.02 3.91   12.4  51.7  1.73                               mg/kg                                                                          100   0.898  0.734  0.526                                                                                0.401 9.12  15.6  0.961                              mg/kg                                                                           50   0.536  0.415  0.357                                                                                0.0386                                                                               7.65  19.0  0.976                              mg/kg                                                                           0    0.715  0.614  0.739                                                                               1.06   11.0  34.1  --                                 mg/kg                                                                          ______________________________________                                    

No antibody response is observed until day 12, when the 200 and 400 mg/kg treatment groups show significant stimulation (four-fold increases) over the control treatment groups. A similar pattern of difference between the controls and treated groups holds on day 17, seven days after cessation of Cpd. 1 treatment, with the 200 and 400 mg/kg doses showing an eight-fold increase over the untreated antigen-sensitized controls.

The lymphocyte proliferation assay is only performed on day 17, some five days subsequent to completion of the Cpd. 1 treatment protocol. A statistically significant increase in lymphocyte DNA synthesis is seen in the 200 mg/kg treated mice stimulated by Con-A or KLH mitogens. The lymphocyte mitogen response to Con-A (T-cell mitogen) correlated well with a positive response to KLH of the KLH sensitized spleen lymphocytes.

EXAMPLE 25

The effect of Cpd. 1 on cytotoxic lymphocyte (CTL) activity is measured using five DBA/2 mice in the early stage of the TDS, 10 days after challenge with viable L5178Y tumor cells. Six doses of Cpd. 1, 0.001, 0.01, 0.1, 1.0, 10, or 100 μg/ml or just buffer are added in 100 μl volumes to MLTC microculture wells containing washed spleen lymphocytes from the DBA/2 mice, effector, and L5178Y target cells at varying E/T ratios. The MLTC reaction is performed in the presence or absence of irradiated L5178Y stimulator cells.

                  TABLE 18-A                                                       ______________________________________                                         Effect of Cpd. 1 on CTL Activity of TDS Spleen Lymphocytes                     from DBA/2 Mice, as Measured by MLTC Assay Using                               Effector Cells Co-cultured with Stimulator Cells                                          % Lysis                                                                        E/T Ratio                                                           Cpd. 1 Conc. 100:1       30:1   10:1                                           ______________________________________                                         100     μg/ml 87.3        54.2 21.2                                         10      μg/ml 74.3        42.0 15.9                                         1.0     μg/ml 71.5        46.0 15.6                                         0.1     μg/ml 79.0        51.0 20.2                                         0.01    μg/ml 77.1        55.8 20.6                                         0.001   μg/ml 71.1        40.2 16.7                                         0       μg/ml 55.2        23.0  8.2                                         ______________________________________                                    

                  TABLE 18-B                                                       ______________________________________                                         Effect of Cpd. 1 on CTL Activity of TDS Spleen Lymphocytes                     from DBA/2 Strain of Mice, as Measured by MLTC Assay                           Using Effector Cells Without Stimulator Cells                                             % Lysis                                                                        E/T Ratio                                                           Cpd. 1 Conc. 100:1       30:1   10:1                                           ______________________________________                                         100     μg/ml 42.0        18.7 8.6                                          10      μg/ml 36.3        16.8 4.6                                          1.0     μg/ml 40.1        20.0 4.6                                          0.1     μg/ml 31.6        14.8 3.5                                          0.01    μg/ml 26.0        15.7 3.5                                          0.001   μg/ml 23.4        12.2 3.9                                          0       μg/ml 22.7        11.0 -2.2                                         ______________________________________                                    

Cpd. 1 causes a significant increase in CTL activity expressed as % lysis at several concentrations irrespective of the E/T ratio employed or whether or not stimulator cells are present.

This data therefore supports amplification of the specific CTL response of TDS mouse spleen cells sensitized to L5178Y tumor cells in a drug dose dependent manner.

EXAMPLE 26

Five DBA/2 mice in the early stage of the TDS, 10 days after challenge with viable L5178Y tumor cells were used to measure the effect of Cpd. 1 on CTL activity. Two doses of Cpd. 1, 10, or 100 μg/ml, or just buffer were added in 100 μl volumes to the MLTC microculture wells containing washed spleen lymphocytes from the DBA/2 mice, effector and L5178Y target cells at varying E/T ratios. The MLTC reaction was performed in the presence or absence of irradiated L5178Y stimulator cells.

                  TABLE 19-A                                                       ______________________________________                                         Effect of Cpd. 1 on CTL Activity of TDS Spleen Lymphocytes                     from DBA/2 Mice, as Measured by MLTC Assay Using                               Effector Cells Co-cultured with Stimulator Cells                                          % Lysis                                                                        E/T Ratio                                                           Cpd. 1 Conc. 50:1   25:1      12.5:1                                                                               6.25:1                                     ______________________________________                                         100 μg/ml 71.6   79.8      75.7  56.3                                        10 μg/ml 75.7   72.0      67.1  60.5                                        0 μg/ml  63.9   61.9      45.0  35.5                                       ______________________________________                                    

                  TABLE 19-B                                                       ______________________________________                                         Effect of Cpd. 1 on CTL Activity of TDS Spleen Lymphocytes                     from DBA/2 Strain of Mice, as Measured by MLTC Assay                           Using Effector Cells Without Stimulator Cells                                            % Lysis                                                                        E/T Ratio                                                            Cpd. 1 Conc.                                                                               50:1    25:1       12.5:1                                                                               6.25:1                                    ______________________________________                                         100 μg/ml                                                                               21.8    16.6       11.1  6.1                                        10 μg/ml                                                                               12.8    8.1        6.9   .7                                         0 μg/ml -7.5    -3.0       -3.5  -1.3                                      ______________________________________                                    

Cpd. 1 caused a significant increase in CTL activity expressed as % lysis, at several concentrations irrespective of the E/T ratio employed or whether or not stimulator cells were present.

EXAMPLE 27

DBA/2 mice in the early stage of TDS, prior to challenge with viable L5178Y tumor cells, were used to measure the effect of Cpd. 2 on CTL activity. Cpd. 2, 0.1, 1.0, 10 or 100 μg/ml, or just buffer was added in 100 μl volumes to MLTC microculture wells containing washed spleen lymphocytes from DBA/2 mice, effector, and L5178Y target cells at varying E/T ratios. The MLTC reaction was performed in the presence or absence of irradiated L5178Y stimulator cells.

                  TABLE 20-A                                                       ______________________________________                                         Effect of Cpd. 2 on CTL Activity of Pre-Challenge TDS                          Spleen Lymphocytes from DBA/2 Mice, as Measured                                by MLTC Assay Using Effector Cells                                             Co-cultured with Stimulator Cells                                                         % Lysis                                                                        E/T Ratio                                                           Cpd. 2 Conc. 100:1  50:1       25:1 12.5:1                                     ______________________________________                                         100    μg/ml  78.5   73.5     65.0 47.0                                     10     μg/ml  73.5   72.5     72.5 58.5                                     1      μg/ml  75.5   72.5     69.5 58.0                                     0.1    μg/ml  74.5   69.5     64.0 47.5                                     0      μg/ml  68.5   67.0     57.0 37.5                                     ______________________________________                                    

                  TABLE 20-B                                                       ______________________________________                                         Effect of Cpd. 2 on CTL Activity of Pre-Challenge                              TDS Spleen Lymphocytes from DBA/2 Mice,                                        as Measured by MLTC Assay Using Effector Cells                                 Without Stimulator Cells                                                                 % Lysis                                                                        E/T Ratio                                                            Cpd. 2 Conc.                                                                               100:1  50:1       25:1 12.5:1                                      ______________________________________                                         10    μg/ml  61.5   56.5     40.0 26.5                                      0.1   μg/ml  48.0   43.5     29.5 16.5                                      0     μg/ml  58.5   49.0     32.5 19.5                                      ______________________________________                                    

Cpd. 2 caused an increase in CTL activity, expressed as % lysis, at several concentrations irrespective of the E/T ratio employed or whether or not stimulator cells were present. The one exception was the 0.1 μg/ml dose when no stimulator cells were present.

EXAMPLE 28

An MLTC assay is performed to assess the CTL activity and tumor target cell specificity of Cpd. 1. Tumor dormant spleen cells and normal spleen cells of DBA/2 mice are used as effector cells. Irradiated L5178Y cells are used as stimulator cells. ⁵¹ Cr-labeled L5178Y cells and FLC-745 cells are used as target cells. The effector/target ratios studied are 100:1, 30:1 and 10:1.

                  TABLE 21                                                         ______________________________________                                         Effect of Cpd. 1 In Vitro, as Measured by                                      MLTC Assay, on TDS and Normal Spleen                                           Cells from the DBA/2 Strain of Mice                                                       % Lysis                                                                        E/T Ratio                                                                      100:1     30:1     10:1                                             ______________________________________                                         Target cell - L5178Y                                                           E + S + D    82.3        69.2     34.9                                         E + S        55.5        39.3     11.4                                         E + D        52.8        29.8     9.0                                          E            50.9        29.2     7.2                                          N + S + D    -9.5        -9.7     -10.9                                        N + S        -14.2       -10.5    -11.2                                        N + D        -12.4       -11.4    -10.3                                        N            -11.2       -11.0    -10.9                                        Target cell - FLC-745                                                          E + S + D    13.4        3.6      0.5                                          E + S        6.9         1.4      -4.0                                         E + D        6.6         4.6      0.7                                          E            11.8        6.6      -1.3                                         N + S + D    5.8         -0.8     -1.1                                         N + S        5.8         1.1      -2.6                                         N + D        13.9        0.9      -3.5                                         N            1.7         -1.8     -2.9                                         ______________________________________                                    

E=Effector, Tumor dormant spleen cells; S=Stimulator, Irradiated L5178Y cells; D=Cpd. 1; N=Normal effector cells, Normal spleen cells.

A significant specific enhancement of CTL activity of effector cells in the presence of stimulator cells was noted in the L5178Y target control system when Cpd. 1 is present. This effect is not observed in the FLC-745 target control system nor did effector cells alone yield an enhancement effect. These results demonstrate the enhancement of the activity of stimulated effector cells by Cpd. 1, the activity of the T-cell memory of the system, and the specificity of the stimulated effector cells.

EXAMPLE 29

The effect of Cpd. 1 on the emergence from the L5178Y tumor dormant state is studied by treating forty DBA/2 mice with Cpd. 1 after the mice have undergone the TDS inducing procedure. Two days after the mice have been challenged with i.p. administration of 50,000 viable L5178Y tumor cells, twenty of these mice receive seven consecutive days of i.p. treatment with Cpd. 1 at 100 mg/kg and the remaining twenty mice receive buffer only. A partial peritoneal lavage is performed twenty-five days after the last dose of Cpd. 1 and the peritoneal exudate fluid is plated out for determination of tumor cell numbers (tumor cell quantitative assay). Survival time is recorded out to 90 days after challenge with the viable L5178Y tumor cells. The percent mortality is calculated for each group.

                  TABLE 22-A                                                       ______________________________________                                         Range Distribution of Tumor Cells in TDS DBA/2 Mice,                           as Measured by Tumor Cell Quantitative Assay                                                        Treated Group                                                      Control Group           % of                                          No. Tumor Cells                                                                           Frequency % of Total                                                                               Frequency                                                                              Total                                   ______________________________________                                         0          1          6        4       22                                      <1,000     6         35        6       33                                      1,000 to 100,000                                                                          8         47        7       39                                      >100,000   2         12        1        6                                      ______________________________________                                    

                  TABLE 22-B                                                       ______________________________________                                         Mortality Statistics for TDS DBA/2 Mice                                        at 90 Days Post-Challenge                                                      Cpd. 1 Concentration                                                                          No. Survivors                                                                              % Survival                                          ______________________________________                                         100 mg/kg      10          55.6                                                 0 mg/kg        3          17.6                                                ______________________________________                                    

There is significant reduction in the numbers of tumor cells recovered from Cpd. 1 treated animals versus the controls. The treated group shows more mice demonstrating lower tumor cell numbers in peritoneal washes. There is a significantly greater survival of these mice treated with Cpd. 1 over untreated controls.

EXAMPLE 30

The effect of Cpd. 1 on the emergence from the L5178Y tumor dormant state was studied by treating forty DBA/2 mice with Cpd. 1 after the mice had undergone the TDS inducing procedure. Two days after the mice were challenged with i.p. administration of 50,000 viable L5178Y tumor cells, twenty of these mice received seven consecutive days of i.p. treatment with Cpd. 1 at 100 mg/kg and the remaining twenty mice received buffer only. A partial peritoneal lavage was performed twenty-five days after the last dose of Cpd. 1 and the peritoneal exudate fluid was plated out for determination of tumor cell numbers (tumor cell quantitative assay). Survival time was recorded out to 114 days after challenge with the viable L5178Y tumor cells. The percent mortality was calculated for each group.

                  TABLE 23-A                                                       ______________________________________                                         Range Distribution of Tumor Cells in TDS DBA/2 Mice,                           as Measured by Tumor Cell Quantitative Assay                                                        Treated Group                                                      Control Group           % of                                          No. Tumor Cells                                                                           Frequency % of Total                                                                               Frequency                                                                              Total                                   ______________________________________                                         0          3         13.0      16      69.6                                    <1,000     8         34.8      2        8.7                                    1,000 to 100,000                                                                          10        43.5      4       17.4                                    >100,000   2          8.7      1        4.3                                    ______________________________________                                    

                  TABLE 23-B                                                       ______________________________________                                         Mortality Statistics for TDS DBA/2 Mice                                        at 114 Days Post-Challenge                                                     Cpd. 1 Concentration                                                                          No. Survivors                                                                              % Survival                                          ______________________________________                                         100 mg/kg      19          82.6                                                 0 mg/kg       11          47.8                                                ______________________________________                                    

There was significant reduction in the numbers of tumor cells recovered from Cpd. 1 treated animals versus the controls. The treated group showed more mice demonstrating lower tumor cells numbers in peritoneal washes. There was a significantly greater survival of mice treated with Cpd. 1 over untreated controls.

EXAMPLE 31

Mice of the BDF₁ strain, inoculated with L-1210 leukemia cells, are treated for seven days with either 25, 50, 100, 200 or 400 mg/kg of Cpd. 1 or just buffer. The National Cancer Institute protocol for screening new anti-cancer agents is followed and T/C ratios are calculated.

                  TABLE 24                                                         ______________________________________                                         Effect of Cpd. 1 on the Treatment of L-1210 Leukemia,                          as Measured by T/C Ratios, in BDF.sub.1 Strain of Mice                         Cpd. 1 Conc.                                                                               Median Survival Time (Days)                                                                       T/C                                             ______________________________________                                         400 mg/kg   25                 1.25                                            200 mg/kg   30                 1.50                                            100 mg/kg   30                 1.50                                             50 mg/kg   21                 1.05                                             25 mg/kg   20                 1.00                                             0 mg/kg    20                 --                                              ______________________________________                                    

The doses of 400, 200 and 100 mg/kg yield T/C values of 1.25, 1.50 and 1.50 respectively, which are considered significant by National Cancer Institute standards of evaluation.

EXAMPLE 32

Mice of the BDF₁ strain, inoculated with L-1210 leukemia cells, are treated for seven days with either 100 mg/kg of Cpd. 1, 20 mg/kg of 5-fluorouracil (5-FU), a known anti-cancer agent, or just buffer. The National Cancer Institute protocol for screening new anti-cancer agents is followed and T/C ratios are calculated.

                  TABLE 25                                                         ______________________________________                                         Effect of Cpd. 1 and 5-FU on the Treatment of L-1210                           Leukemia, as Measured by T/C Ratios, in BDF.sub.1 Strain of Mice               Drug    Conc.       Median Survival Time                                                                          T/C                                         ______________________________________                                         Cpd. 1  100 mg/kg   28             1.40                                        5-FU     20 mg/kg   30             1.50                                        Buffer  --          20             --                                          ______________________________________                                    

The 100 mg/kg Cpd. 1 treatment dose yields a T/C value of 1.40 compared to 1.50 for the 5-FU positive control. This data substantiated the positive findings of Example 31 and also compares the anti cancer results observed after use of Cpd. 1 to the results observed after use of an accepted positive control drug, 5-FU. 

What is claimed is:
 1. A compound of the formula ##STR16## wherein: R₂ is selected from the group consisting of hydrogen and lower alkyl;R₅ and R₆ are selected from the group consisting of hydrogen and lower alkyl and may be the same or different; R₈ is selected from the group consisting of hydrogen and lower alkyl; R₇ is hydrogen, lower alkyl or ##STR17## R₉ is CH₂ OH R₁₀ is hydrogen; consisting of hydrogen, lower alkyl, phenyl and hydroxyl substituted loweralkyl and may be the same or different; when R₇ contains a hydroxyl group in the α or β position, R₇ may form the hemiketal ring closure at the carbon 3 of the butyrolactone with protonation of the carbonyl group on the same carbon atom; and X is selected from the group consisting of O, S, and NH.
 2. The compound of claim 1 having the structure formula ##STR18## wherein: R₂ is --CH₃ ;R₅ and R₆ are each hydrogen; X is O; R₈ is as defined in claim
 1. 3. A crystalline molecular complex, comprising the compound of claim 2 and succinic anhydride in a molar ratio of 2:1.
 4. A crystalline molecular complex, comprising the compound of claim 2 and succinimide in a molar ratio of 2:1.
 5. A crystalline molecular complex, comprising the compound of claim 2 and N-methyl succinimide in molar ratio of 2:1. 